Embryology Flashcards
What is the neck developed from?
Branchial/pharyngeal arches
What is the face developed from?
5 mesenchymal processes/prominences
What is the skull developed from?
Mesenchyme in the head region of the developing embryo
What is mesenchyme?
Embryonic connective tissue
Same properties as connective tissue
Develops into bone, cartilage, blood vessels etc
How is mesenchyme formed?
Neural crest cells in the head and neck region mix with mesoderm = mesenchyme
What is the role of somites in the development of head and neck?
Somites in head region of embryo help in cranial skeleton development
What are pharyngeal/branchial arches?
Series of arches which develop around future mouth and pharynx
How many branchial arches are there?
6 arches start to develop but arch 5 disappears
Left with 1, 2, 3, 4 and 6
What embryological tissues make up the branchial arches?
Ectoderm = outside + clefts between arches Mesoderm = middle = cartilage, muscles Endoderm = inside = pouches between arches
What nerve does the 1st branchial arch form?
Mandibular branch of trigeminal
What nerve does the 2nd branchial arch form?
Facial
What nerve does the 3rd branchial arch form?
Glossopharyngeal
What nerve does the 4th branchial arch form?
Superior laryngeal branch of vagus
What nerve does the 6th arch of the branchial arches form?
Recurrent laryngeal branch of vagus
What type of innervation does the glossopharyngeal supply to the parotid salivary gland?
Parasympathetic
What is the anterior belly of the digastric muscle innervated by?
Mandibular division of trigeminal nerve (V3)
What is the posterior belly of the digastric muscle innervated by?
Facial nerve
What other important structures develop from the branchial arches?
Tongue
Thyroid gland
Parathyroid gland
Part of the pituitary gland
What are the 5 processes that the face develops from?
1 frontonasal process
2 maxillary processes
2 mandibular processes
How does the nostril form?
Ectodermal thickening pushes nwards/invaginates to form the nasal pit
How is the philtrum formed?
Medial nasal process grows downwards and laterally
How is the palate developed?
Development of the philtrum = primary palate
Maxillary processes = 2 palatine shelves grow inwards
Palatine shelves meet in midline to form secondary palate
How is the cranial vault (flat bones) formed?
Membranous bones = formed by membranous ossification calvaria
How is the base of the skull (irregular bones) formed?
Bones formed by endochondral ossification
How is the viscerocranium (skeleton of face) formed?
Partly from branchial arches and partly from sensory (special sense) capsules
What age does the anterior fontanelle close?
1.5 years
What is the reason for the sutures between skull bones being soft?
Allows deformation during passage through birth canal
What happens in craniosynostosis?
When the skull fuses too early
Doesn’t leave room for the brain to grow
Misshapen skull
What are sensory capsules?
Derived from mesoderm of somites in head and neck region
Preform in cartilage and ossify to form bones around sense organs (e.g. nose, eye, ear)
Partly base of skull, partly viscerocranium
